In almost every way that matters, Rowan Jimenez's life has returned to normal in the four years since he had two new lungs transplanted into his chest.

He regularly bikes 7 miles to his job in Richmond, and he runs and rock climbs. He sings with a band and plays with his active 9-year-old daughter. Every day, he breathes deeply and thinks how lucky he is.

But Jimenez, like almost all lung transplant patients, is also keenly aware how short life can be. And while lung transplants have become increasingly common - and increasingly successful - over the past decade, they're still among the riskiest transplant procedures. Patients have only slightly better than even odds of surviving five years after a transplant.

"A lot of people say that when you hit the five-year benchmark, it's downhill from there," said Jimenez, 44, who has a condition called scleroderma that led to him getting a double lung transplant at UCSF in September 2008. "But I've met people who are nine or 10 years post transplant. So I'm looking forward to four more years - 10 more, 20 more."

Survival rates after 1st year

Jimenez may very well have a decade or more left on what he calls his "recycled" lungs, but the numbers aren't in his favor, and overall survival rates have improved by only about 5 percent over the past 10 years.

About 1,400 lung transplants are performed in the United States every year - including about 150 at UCSF and Stanford, the two Bay Area institutions that do the procedures - and roughly 90 percent of those patients will live at least one year after the procedure. The one-year survival rates are 94 percent and 90 percent at UCSF and Stanford, respectively.

But after that first year, the survival rates dip dramatically, both nationally and locally. Only about 55 percent of patients survive five years after the transplant. Those rates are better at Bay Area hospitals, where about two-thirds of patients can expect to survive that long. Nationwide, only a third of patients live 10 years.

It's unclear what, exactly, goes wrong after the first year. Most patients die of what's known as chronic rejection, which causes the airways of the lung to deteriorate slowly. Doctors don't yet know how to prevent or stop that process.

"I started doing (lung transplants) in the early '90s, and it was really primitive then, and it's gotten a lot better. All sorts of things have improved," said Dr. David Weill, director of Stanford's Center for Advanced Lung Disease. "But we haven't solved the mystery of that slow loss of lung function."

Lung transplants are notoriously difficult, both during the surgery and in the months and years after the transplant. That's in part because of the fact that the lungs are one of the only major organs that are regularly exposed, through every inhalation, to the outside environment, and that makes them especially vulnerable to infection.

The lungs were among the last of the human organs to be successfully transplanted after multiple failed attempts in the 1960s and '70s. In the 1980s, doctors finally conquered some of the problems, such as infection and rejection, that killed most patients within days or weeks of a transplant. Since then, one-year survival rates have improved dramatically and lung transplants are far more common.

More lungs, alternatives

Surgeons are now able to transplant donated lungs that once would have been disposed of because of injury or infection. They're also able to treat patients who, in the past, would have been considered too sick to get a transplant. Doctors are using new immunosuppressant drugs to prevent organ rejection, and they've learned how to better minimize infection both during the surgery and in the vulnerable months just afterward.

Seven years ago, the national Organ Procurement and Transplant Network introduced a new system for allocating lungs that no longer gives preference to patients who have been waiting the longest. The result is that the organs are much more widely available to a larger group of patients.

Vast differences in severity

Transplants given on a first-come, first-served basis may be a reasonable way to allocate organs for things like kidney disease, which patients can live with for years or even decades. But for lung patients, there are vast differences in severity of disease. While some patients can survive for years without a transplant, others may have only days or weeks after a diagnosis.

Before the changes were made, the waiting list for a lung transplant was about two years, and about 500 people nationwide would die every year while waiting for one. After the new allocation system was established in 2005, the wait time dropped to three or four months, and the number of deaths was cut in half.

"Generally, the sickest patients get transplanted first now," said Dr. Steven Hays, medical director for the lung transplantation program at UCSF. That's had a huge impact in particular on patients with idiopathic pulmonary fibrosis, a disease that causes scarring of the lungs for no known reason.

"It tends to be a relentless disease that can progress very rapidly. Someone can go from walking to being totally oxygen dependent in a few months," Hays said. "In the old days, you'd have to wait two years for a transplant, so that was basically a death sentence for those patients."

Now, patients with pulmonary fibrosis make up more than half of the lung transplants at UCSF, he said.

What's helped reduce the wait time, organ transplant experts say, is that many of the institutions that do lung transplants have become much more aggressive in accepting donated lungs.

Lungs are a difficult organ to harvest because they're so easily injured and vulnerable to infection. When donors are brain-dead, which is often the case, they're kept on a ventilator to maintain oxygen in the blood supply going to their still-healthy organs. But ventilators can damage the lungs, and they often promote infections such as pneumonia.

Only about 1 in 5 lungs from deceased donors is viable for transplantation. Dr. Jasleen Kukreja, surgical director of the lung transplant program at UCSF, said doctors have worked out techniques to recover some of those lungs, including treating infections after the organs have been removed. UCSF expects to start using a new technique next year that involves placing injured donor lungs into a machine that will pump blood and nutrients into them and repair them before they are transplanted.

But much work remains if doctors and surgeons are going to improve long-term survival rates. Many lung recipients experience a sudden and remarkable improvement in their health after their surgery, only to end up gasping for breath again in four or five years.

1st breath with new lungs

Jimenez still remembers clearly, despite the fog of pain medications and anesthesia, what it was like to take his first breath after getting his new lungs.

"It was like, just yesterday I was dying, I could barely breathe, and today, nine hours later, I'm breathing like a normal person again," he said. "It took a few days to set in. Every day I would wake up and slowly breathe and think, 'Is this for real?' "

Video on life of lung transplant patient

Rowan Jimenez made a video about his life before and after his double lung transplant. To watch, go to www.vimeo.com/2570874.